Dissertations / Theses on the topic 'Polymer nanocomposites'
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Su, Xing. "Polymer/montmorillonite nanocomposites : polyamide 6 nanocomposites and polyacrylamide nanocomposite hydrogels." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18366/.
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Polymer/clay nanocomposites have attracted great attention of researchers for two decades because they are light in weight, easy to be fabricated, and have some unique properties such as thermal barrier and corrosion resistant. Montmorillonite (MMT) is frequently chosen as the clay filler for polymer/clay nanocomposites because of its abundance, high functionality and high cation exchange capacity. This project aims to prepare novel polymer/MMT nanocomposites with adjustable microstructure, good mechanical properties and unique stimuli-sensitive properties. As the control over the clay intercalation/exfoliation ratio is difficult for the polymer/clay nanocomposites, the effect on clay exfoliation of polyamide 6/MMT nanocomposites by using a chemical blowing agent (CBA), citric acid, during extrusion was studied. X-ray diffraction confirmed that the decomposition of CBA did improve clay exfoliation. As many surfactants used for treating clay surface are likely to degrade during the melt processing of polymer/MMT nanocomposites, a novel thermally stable surfactant was used. Polyamide 6/MMT nanocomposites were prepared by either twice or triple extrusion. And the effect on the mechanical properties and thermal stability were studied. The incorporation of clays increased Young’s modulus but decreased strain at break. There was no significant improvement on the thermal stability by the incorporation of clays and/or CBA. Polymer nanocomposite hydrogels often showed high hysteresis when subject to cyclic tension, and their mechanical properties were hardly tested at the fully swollen state. Therefore a novel polyacrylamide (PAM)/polysaccharide-treated MMT nanocomposite hydrogel with low cyclic tensile hysteresis was successfully prepared by in situ polymerisation. This was shown to be stretchable, tough and highly compression-resistant at the fully swollen state. An interpenetrating nanocomposite hydrogel using PAM, MMT, alginate and Ca2+ was proposed in the same chapter. At the fully swollen state, apart from the good mechanical properties such as stretchability, toughness and resilience, it displayed significantly pH-dependant shape changes. As for the current alginate/MMT nanocomposites in the literature, only the mechanical properties under the dry state were studied. The mechanical properties of the fully swollen alginate/MMT/Ca2+ nanocomposite were investigated. The nanocomposite films turned out to be stiff, strong and transparent. Also some of the nanocomposite films were ultraviolet light-proof or sensitive to acetone. Based on the above findings, it is concluded that: firstly, there was a large amount of residual citric acid in the extruded materials, which reduced the mechanical properties and thermal stability of polyamide 6/MMT nanocomposites. Secondly, the thermally stable polymeric surfactant has the potential of enhancing the toughness and thermal stability of polyamide 6/MMT nanocomposites. Thirdly, it was likely to achieve low cyclic-tensile hysteresis, high strength, high toughness and stimuli-responsivity by the polymer/clay nanocomposite hydrogels at the fully swollen state. Those nanocomposite hydrogels can be used in a variety of applications including artificial tissues, medicine, agriculture, skin care and other aquatic uses.
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Mohagheghian, Iman. "Impact response of polymers and polymer nanocomposites." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648854.
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Mohaddes, pour Ahmad. "Granular polymer nanocomposites." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117135.
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Contrary to classical theories, nanoparticle dispersion in polymer melt has been shown to decrease the bulk viscosity, and to increase the membrane permeability and selectivity when incorporated into certain amorphous polymer glasses. However, the effects of particle concentration, particle size, and polymer configuration at particle interfaces are not well understood. To elucidate how the particle size, chain length, and mixture composition influence polymer-chain packing and, thus, free volume---which is known to primarily influence rheological and permeation properties of polymer nanocomposites---the volume of acrylic spheres (representing nanoparticles) mixed with aluminum ball chains (representing polymer chains) was measured, and the partial molar sphere volume at small but finite sphere volume fractions was calculated. The results show that the sphere radius with respect to the minimum chain loop size is the primary dimensionless parameter that affects mixture free volume. Moreover, free volume is maximal---up to twice the intrinsic inclusion volume per particle---when the sphere radius and the minimum chain loop size are comparable, which is because of the increase in sphere-chain interactions, whereas sphere-sphere interactions decrease the mixture free volume when particles are large. It was further determined that, in the presence of nanoparticles, free volume and polymer chain architecture play a determinative role in influencing the glass transition temperature of polymer nanocomposites. The reason for the decrease in the glass transition temperature of polymer nanocomposites is known to be the repulsive chain-nanoparticle interactions. However, in the absence of enthalpic interactions, it is still elusive how and why the glass transition temperature declines with nanoparticle loading. To examine the nanoparticle influence on chain relaxation dynamics and, thus, nanocomposite glass transition temperature, the relaxation time (the time to reach the close-packed, jammed state) of granular chain-sphere mixtures was measured by systematically changing the sphere size, chain length, and mixture composition. Measuring the compaction dynamics reveals that spherical inclusions profoundly influence the chain relaxation time when the characteristic nanoparticle separation and nanoparticle size are comparable to the chain loop size. This study can shed light on polymer architecture in the presence of nanoparticles, especially when chains are very long and, thus, beyond the capability of current computer simulations. This macroscopic, granular model can also be used to optimize the design of polymer nanocomposites by a judicious choice of nanoparticle size, chain length, and mixture composition for industrial and biomedical applications.Contrairement aux théories classiques, les nanoparticules ont été utilisées pour diminuerla viscosité de volume lorsqu'elles sont dispersées dans un mélange de polymère, et pour augmenter la perméabilité de la membrane et la sélectivité lorsqu'elles sont incorporées dans certains verres polymères amorphes. Cependant, les effets sur la concentration des particules, sur la taille des particules et sur la configuration des polymères à particules inter faciales ne sont pas bien compris. Afin de comprendre comment la taille des particules, la longueur de la chaîne, et les différentes compositions influencent l'assemblage des chaines de polymères et, par conséquent, le volume libre — qui est connu principalement pour agir sur les propriétés rhéologiques et d'infiltration despolymères nanocomposites—le volume de sphères acryliques (représentant les nanoparticules) couplé avec les chaînes de billes d'aluminium (ce qui représente des chaînes de polymère) a été mesurée, et le volume molaire partiel des sphères a été calculée à partir depetit volume fini . Les résultats montrent que le rayon de la sphère par rapport à la taille dela boucle de la chaîne minimum est le paramètre qui affecte principalement la dimensiondu volume de mélange libre. De plus, le volume libre est maximale—jusqu'à deux fois levolume de l'inclusion intrinsèque par particule—lorsque le rayon de la sphère et la taille minimum de la boucle de la chaîne sont comparables, ce qui est d à l'augmentation des interactions dans la chaîne de la sphère, alors que les interactions sphère-sphère diminuent le volume du mélange libre lorsque les particules sont grandes. Il a également été déterminé que, en présence de nanoparticules, le volume libre et l'architecture de la chaîne du polymère jouent un rôle déterminant en influençant la température de transition vitreuse des polymères nano composites. La raison ostensible pour la diminution dela température de transition vitreuse des polymères nano composites est connue pour tre la répulsion entre les chaînes des nanoparticules. Toutefois, en l'absence d'interactions enthalpiques, c'est encore élusif de comment et pourquoi la température de transition vitreuse baisse avec le chargement des nanoparticules. Pour étudier l'influence des nanoparticules sur la dynamique de relaxation de la chaîne et, par conséquent, la température de transition de verre nanocomposite, le temps de relaxation (le temps d'atteindre l'état bloqué) de la chaine du mélange de granulés a été mesurée en changeant systématiquement la taille et la longueur de la sphère et le mélange de la composition. D'avoir mesurer la dynamique de compactage révèle que les inclusions sphériques influencent profondément le temps de relaxation de la chaîne lors de la séparation des nanoparticules caractéristiques ainsi que la taille des nanoparticules est comparable à la taille de la boucle de chaîne. Cette étude nous éclaire sur l'architecture des polymères en présence de nanoparticules, en particulier lorsque les chaînes sont très longues et par conséquent, au-delà de la capacité des simulations informatiques actuels pour être explorées à fond. Ce modèle macroscopique granulaire peut aussi être utilisé pour optimiser la conception de polymères nanocomposites par un choix judicieux de la taille des nanoparticules, de la longueur de la chaîne et la composition du mélange pour des applications industrielles et biomédicales.
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Chen, Biqiong. "Polymer-clay nanocomposites." Thesis, Queen Mary, University of London, 2004. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1854.
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Polymer-clay nanocomposites are attracting global interest principally because property enhancements are obtained at low clay particle loadings (1-5 wt%). However there is lack of fundamental understanding of such composites. The aim of this work is to provide an insight into the interaction between polymer and clay. This includes the driving force for intercalation, the reinforcement mechanisms and property-volume fraction relationships. Functionalised poly(ethylene glycol)-clay, poly(c-caprolactone)-clay and thermoplastic starch-clay nanocomposites with a range of polymer molecular weights, clay volume fractions and with different clays were prepared using solution methods, melt-processing methods, and in situ polymerisation. A reliable X-ray diffraction technique for low angle basal plane spacing of clay, the essential parameter for structure determination, was established obtaining ±0.005 Mn between three diffractometers. The basal plane spacing was found to be unaffected by polymer molecular weight and preparation method but was affected by the nature of the polymer and clay. Increasing clay loading could lead to a lower spacing. As a cautionary observation, poly(ethylene glycol) with high molecular weight (2: 10,000) was found to undergo degradation readily during preparation of nanocomposites with and without clay. Competitive sorption experiments for molecular weight showed that high molecular weight fractions of polymer intercalate preferentially into clay during solution preparation. Thermodynamic studies on the intercalation process found that significant enthalpic change occurred during intercalation, which is coincident with the observation that heat-treated clays without interlayer water can intercalate polymer. The calculation of true volume fraction against nominal volume fraction provided reasonable explanation of property enhancement and helps understand the relation between nanocomposites and conventional composites. At a given clay loading, nanocomposites with better dispersion gave more property enhancement than those with lower dispersion or conventional composites. The crystallinity of semicrystalline polymer was also affected by varying extents of dispersion of clay. The use of X-ray diffraction with an internal standard was explored for quantitative analysis of intercalation and exfoliation.
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Paul, Anita N. "Silver-Polymer Nanocomposites." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etd/3077.
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The objective of this research was the development of an efficient method for the preparation of silver-polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by thiolation with 2-aminoethanethiol. Amino-modified nanosilver was covalently bonded to polyacrylic acid, biodegradable polymers like acid terminated polylactic acid, ester terminated poly(DL-lactide-co-glycolide) and acid terminated poly(DL lactide-co-glycolide) in the presence of diisopropylcarbodiimide by carbodiimide method. Esterification of the carboxyl groups of Ag-polyacrylic acid by hydrochloric acid in methanol resulted in the formation of a stable colloidal dispersion of Ag nanoparticles in the polymer matrix. It was observed that not just acid terminated polymers but also ester terminated polymers could react with functionalized nanosilver. This unusual reaction was due to the aminolysis of the ester bond in the polymer chain by the surface amino groups. Silver-polymer nanocomposites obtained with acid terminated polylactic acid and poly(DL-lactide-co-glycolide) contained highly dispersed nanosilver in the polymer matrix in comparison with the ester terminated poly(DL-lactide-co-glycolide). Chemical and structural characteristics of the obtained materials were studied by instrumental methods. Attained biodegradable materials confirmed X-ray contrast and bactericidal properties, which could be eventually used for biomedical applications.
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Mendez, James D. "Conjugated Polymer Networks and Nanocomposites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1282841324.
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Gurun, Bilge. "Deformation studies of polymers and polymer/clay nanocomposites." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37118.
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Polymer clay nanocomposites have been a popular area of materials research since they were first introduced in the 1990s. The inclusion of clays into many different host polymers has been shown to improve the properties of matrix polymers in a number of ways including increased mechanical strength, thermal stability and improved barrier properties while keeping the composite light weight and transparent. Although there is a great deal of published work on the preparation and property measurements of polymer clay nanocomposites, there is no model to design a nanocomposite with a given set of properties for a specific end-use. While it is important to know the structure property relationships of materials, the understanding of how nanocomposites reach their final forms and properties is equally important. A thorough understanding of processing effects on the final structure of polymer clay nanocomposites is still missing. With this perspective, this thesis addresses building structure-processing relationships of polymer clay nanocomposites by analyzing multiaxial deformation behavior using in-situ x-ray scattering techniques.
This thesis can be divided into two distinct parts. The first part concerns the design of the in-situ multiaxial deformation device (IMDD) used to create the deformation conditions that polymers go through during processing such as blow molding and thermoforming. The device was designed to overcome several concerns with in situ measurement by maintaining constant sample to detector distance, minimizing the material between the incident beam and the detectors, as well as exposing the same point on the sample throughout deformation. A new design to create biaxial deformation, termed in-situ biaxial deformation device (IBDD), is also introduced in this part of the thesis.. In addition, a new heating unit, attached to IBDD, is designed for higher temperature studies, up to 150°C, to imitate industrial processing conditions more closely.
The second part of the thesis addresses the effect of strain, strain rate, and temperature as well as the amount of clay on the polymer morphology evolution during multiaxial deformation.. Two different polymer/clay systems were studied: poly(ethylene)/clay and poly(propylene)/clay. It was observed that the morphological evolution of polyethylene and polypropylene is affected by the existence of clay platelets as well as the deformation temperature and the strain rate. Martensitic transformation of orthorhombic polyethylene crystals into monoclinic crystal form was observed under strain but is hindered in the presence of clay nanoplatelets. The morphology evolution of poly(propylene) crystal structure during multiaxial deformation was more subtle where the most stable α-crystalline form went through strain induced melting. This was more noticeable in the nanocomposites with clays up to 5 wt%.
It was also noted that the thickness of the interlamellar amorphous region increased with increasing strain at room temperature due to the elongation of the amorphous chains. The increase in the amorphous layer thickness is slightly higher for the poly(ethylene)/clay nanocomposites compared to neat poly(ethylene) while the increase in the lamellar long spacing is slightly higher for the neat poly(propylene) compared to poly(propylene)/clay nanocomposites. The rate of change in the characteristic repeat distance in both poly(ethylene) and poly(propylene) systems is higher at faster strain rates, at room temperature, where it remained constant during higher temperature deformations.
Time dependent recovery after deformation studies have shown that poly(ethylene)/clay system reverts back to its initial configuration. The recovery in the amorphous chains was however observed to take longer in the clay added poly(ethylene)s. Crystalline relaxation was observed to happen almost instantly in the poly(ethylene)/clay system. On the other hand, amorphous chains in the poly(propylene)/clay system did not revert back to the initial configuration in the period of time that the recovery observations were performed while the crystalline configuration recovered back almost fully in the given time.
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Chirowodza, Helen. "Polymer-clay nanocomposites prepared by RAFT-supported grafting." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71914.
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Thesis (PhD)--Stellenbosch University, 2012.ENGLISH ABSTRACT: In materials chemistry, surface-initiated reversible deactivation radical polymerisation (SI-RDRP) has emerged as one of the most versatile routes to synthesising inorganic/organic hybrid materials consisting of well-defined polymers. The resultant materials often exhibit a remarkable improvement in bulk material properties even after the addition of very small amounts of inorganic modifiers like clay. A novel cationic reversible addition–fragmentation chain transfer (RAFT) agent with the dual purpose of modifying the surface of Laponite clay and controlling the polymerisation of monomer therefrom, was designed and synthesised. Its efficiency to control the polymerisation of styrene was evaluated and confirmed through investigating the molar mass evolution and chain-end functionality. The surface of Laponite clay was modified with the cationic chain transfer agent (CTA) via ion exchange and polymerisation performed in the presence of a free non-functionalised CTA. The addition of the non-functionalised CTA gave an evenly distributed CTA concentration and allowed the simultaneous growth of surface-attached and free polystyrene (PS). Further analysis of the free and grafted PS using analytical techniques developed and published during the course of this study, indicated that the free and grafted PS chains were undergoing different polymerisation mechanisms. For the second monomer system investigated n-butyl acrylate, it was apparent that the molar mass targeted and the monomer conversions attained had a significant influence on the simultaneous growth of the free and grafted polymer chains. Additional analysis of the grafted polymer chains indicated that secondary reactions dominated in the polymerisation of the surface-attached polymer chains. A new approach to separating the inorganic/organic hybrid materials into their various components using asymmetrical flow field-flow fractionation (AF4) was described. The results obtained not only gave an indication of the success of the in situ polymerisation reaction, but also provided information on the morphology of the material. Thermogravimetric analysis (TGA) was carried out on the polymer-clay nanocomposite samples. The results showed that by adding as little as 3 wt-% of clay to the polymer matrix, there was a remarkable improvement in the thermal stability.
AFRIKAANSE OPSOMMING: Oppervlakgeïnisieerde omkeerbare deaktiveringsradikaalpolimerisasie (SI-RDRP) is een van die veelsydigste roetes om anorganiese/organiese hibriedmateriale (wat bestaan uit goed-gedefinieerde polimere) te sintetiseer. Die produk toon dikwels ʼn merkwaardige verbetering in die makroskopiese eienskappe – selfs na die toevoeging van klein hoeveelhede anorganiese modifiseerders soos klei. ʼn Nuwe kationiese omkeerbare addisie-fragmentasie kettingoordrag (RAFT) middel met die tweeledige doel om die modifisering van die oppervlak van Laponite klei en die beheer van die polimerisasie van die monomeer daarvan, is ontwerp en gesintetiseer. Die klei se doeltreffendheid om die polimerisasie van stireen te beheer is geëvalueer en bevestig deur die molêre massa en die funksionele groepe aan die einde van die ketting te ondersoek. Die oppervlak van Laponite klei is gemodifiseer met die kationiese kettingoordragmiddel (CTA) deur middel van ioonuitruiling en polimerisasie wat uitgevoer word in die teenwoordigheid van ʼn vrye nie-gefunksionaliseerde CTA. Die toevoeging van die nie-gefunksionaliseerde CTA het ʼn eweredig-verspreide konsentrasie CTA teweeggebring en die gelyktydige groei van oppervlak-gebonde en vry polistireen (PS) toegelaat. Verdere ontleding van die vrye- en geënte PS met behulp van analitiese tegnieke wat ontwikkel en gepubliseer is gedurende die verloop van hierdie studie, het aangedui dat die vry- en geënte PS-kettings verskillende polimerisasiemeganismes ondergaan. n-Butielakrilaat is in die tweede monomeer-stelsel ondersoek en dit was duidelik dat die molêre massa wat geteiken is en die geënte polimeerkettings. ʼn Nuwe benadering tot die skeiding van die anorganiese/organiese hibriedmateriale in hulle onderskeie komponente met behulp van asimmetriese vloeiveld-vloei fraksionering (AF4) is beskryf. Die resultate wat verkry is, het nie net 'n aanduiding gegee van die sukses van die in-situ polimerisasiereaksie nie, maar het ook inligting verskaf oor die morfologie van die materiaal. Termogravimetriese analise (TGA) is uitgevoer op die polimeer-klei nanosaamgestelde monsters. Die resultate het getoon dat daar 'n merkwaardige verbetering in die termiese stabiliteit was na die toevoeging van so min as 3 wt% klei by die polimeermatriks.
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Liu, Yi. "Mesoporous silica/polymer nanocomposites." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31739.
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Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.Committee Chair: Jacob. Karl; Committee Member: Griffin. Anselm; Committee Member: Tannenbaum. Rina; Committee Member: Thio. Yonathan S; Committee Member: Yao. Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Bilotti, Emiliano. "Polymer / Sepiolite Clay Nanocomposites." Thesis, Queen Mary, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522330.
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Isitman, Nihat Ali. "Flame Retardancy Of Polymer Nanocomposites." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614258/index.pdf.
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This thesis is aimed to understand the role of nanofiller type, nanofiller dispersion, nanofiller geometry, and, presence of reinforcing fibers in flame retardancy of polymer nanocomposites. For this purpose, montmorillonite nanoclays, multi-walled carbon nanotubes, halloysite clay nanotubes and silica nanoparticles were used as nanofillers in polymeric matrices of poly (methyl methacrylate) (PMMA), high-impact polystyrene (HIPS), polylactide (PLA) and polyamide-6 (PA6) containing certain conventional flame retardant additives. Furthermore, the influence of nanofiller and flame retardant additives on fiber/matrix interfacial interactions was studied.
Materials were prepared by twin-screw extrusion melt-mixing and ultrasound-assisted solution-mixing techniques. Characterization of nanocomposite morphology was done by X-ray diffraction and transmission electron microscopy. Flame retardancy was investigated by mass loss cone calorimetry, limiting oxygen index measurements and UL94 standard tests. Flame retardancy mechanisms were revealed by characterization of solid fire residues by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and X-ray diffraction. Thermal degradation and stability was studied using thermogravimetric analysis. Mechanical properties were determined by tension tests and fracture surfaces were observed under scanning electron microscope.
Influence of nanofiller type was investigated comparing the behavior of montmorillonite nanoclay and multi-walled carbon nanotube reinforced PMMA nanocomposites containing phosphorous/nitrogenous intumescent flame retardant. Carbon nanotubes hindered the formation of intumescent inorganic phosphate barrier which caused the samples to be exposed to larger effective heat fluxes during combustion. Contrarily, nanoclays physically reinforced the protective barrier without disrupting the intumescent character, thereby allowing for lower heat release and mass loss rates, and increased amounts of residue upon combustion.
Influence of nanofiller dispersion was studied comparing nanocomposite and microcomposite morphologies in montmorillonite nanoclay reinforced HIPS containing aluminum hydroxide flame retardant. Relative to microcomposite morphology, reductions in peak heat release rates were doubled along with higher limiting oxygen index and lower burning rates with nanocomposite formation. Improved flame retardancy was attributed to increased amounts of char residue and lower mass loss rates. Nanocomposite formation allowed for the recovery of tensile strength reductions caused by high loading level of the conventional flame retardant additive in polymer matrix.
Influence of nanofiller geometry was investigated for phosphorus based intumescent flame-retarded PLA nanocomposites. Fire performance was increased in the order of rod-like (1-D) <spherical (0-D) <
<
plate-like (2-D) geometries which matched qualitatively with the effective surface area of nanoparticles in the nanocomposite. Well-dispersed plate-like nanoparticles rapidly migrated and accumulated on exposed sample surface resulting in the formation of strong aluminum phosphate/montmorillonite nanocomposite residue. Mechanical properties were increased in the order of 0-D <
1-D <
2-D nanofillers corresponding to the order of their effective aspect ratios in the nanocomposite. Influence of fiber reinforcement was studied for montmorillonite nanoclay containing short-glass fiber-reinforced, phosphorus/nitrogen based flame-retarded PA6 composites. Substitution of a certain fraction of conventional additive with nanofiller significantly reduced peak heat release rate, delayed ignition and improved limiting oxygen index along with maintained UL94 ratings. Improved flame retardancy was ascribed to the formation of a nanostructured carbonaceous boron/aluminum phosphate barrier reinforced by well-dispersed montmorillonite nanolayers. Fiber/matrix interfacial interactions in flame-retarded PA6 and HIPS containing nanoclays were investigated using a micromechanical approach, and it was found that the influence of nanoclay on the interface depends on crystallinity of polymer matrix. While the fiber/matrix interfacial strength is reduced with nanoclay incorporation into amorphous matrix composites, significant interfacial strengthening was imparted by large surface area, well-dispersed clay nanolayers acting as heterogeneous nucleation sites for the semi-crystalline matrix.
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Brown, Elvie Escorro. "Bacterial cellulose/thermoplastic polymer nanocomposites." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Spring2007/e_brown_050207.pdf.
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Hasell, Tom. "Synthesis of metal-polymer nanocomposites." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/10495/.
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This thesis details the synthesis and characterisation of novel nanocomposite materials. The unifying theme of all the projects investigated, is the aim to combine metal or metal oxide nanoparticles with polymer systems. In order to investigate the structure of the materials produced, the extensive use of advanced electron microscopy techniques is essential throughout. Chapter 1: This introductory chapter outlines key themes that are relevant to all the areas of research in this thesis. Theory, background and applications are provided for the fields of nanoparticles, polymers, and supercritical fluids. Chapters 2, 3 and 4 each report a separate area of research. In each chapter additional theory and background is provided where appropriate, and previous literature is discussed. The aims, results and discussion of each research area are contained within the relevant chapter, as well as conclusions and future work. Chapter 2: Supercritical CO2 is used to impregnate optical polymer substrates with silver complexes, which are then decomposed to form nanoparticles. Chapter 3: Metal oxide nanoparticles are used to stabilise dispersion and suspension polymerisations, providing a method of recovering nanoparticles from aqueous solutions and embedding them on the surface of polymer powders. Chapter 4: Two alternative routes, for creating polymer microspheres surface decorated with silver nanoparticles, are compared. Chapter 5: A detailed description of the synthetic methods, equipment, and analysis techniques used in this research is provided. Chapter 6: A brief but overall conclusion to the research is given.
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Elbasuney, Sherif. "Enhanced flame retardant polymer nanocomposites." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14587/.
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Fire is a continuous threat to life and property. The total annual UK fire loss is estimated to be 0.25% of its gross domestic product (GDP) (Goddard, 1995). According to fire statistics, more than 12 million fires break out every year in the United States, Europe, Russia, and China killing about 166,000 people and injuring several hundreds of thousands (Morgan and Wilkie, 2007). Polymers which take up 80% of the organic chemical industry, are known for their high flammability with the production of heat, corrosive toxic gases, and smoke (Bent, 2010). Improving the fire retardancy of polymeric materials is a major concern and also a major challenge. Nanotechnology could have a significant impact on polymeric materials through the achievement of polymer nanocomposites (PNs) with enhanced functional properties (Giannelis, 1996, Schartel and Batholmai, 2006). If this can be achieved, there will be an enormous increase in the use of improved flame retardant (FR) PNs in mass transportation, aerospace, and military applications where fire safety will be of utmost importance (Horrocks and Price, 2008). In this research project nanoparticles that could have a synergistic effect with traditional FR systems, or that could have a FR action (nano-fire extinguishers), were formulated and surface modified during continuous hydrothermal synthesis (CHS). The bespoke nanoparticles were developed in a structure that could be easily integrated and effectively dispersed into a polymeric matrix. A solvent blending approach for integrating and dispersing colloidal organic modified nanoparticles into polymeric matrices was developed. The impact of nanoparticles of different morphologies including nanospheres, nanoplates, and nanorods on epoxy mechanical, thermal, and flammability properties was evaluated. A laboratory based technique using a Bunsen, video footage, and image analysis was developed to quantify the nanocomposite's direct flame resistance in a repeatable fashion. A new self extinguishing epoxy nanocomposite was developed which showed an enhanced performance in extreme conditions and with good mechanical properties.
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Belashi, Azita. "Percolation Modeling in Polymer Nanocomposites." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302196468.
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Burgos, Marmol Jose Javier. "Molecular simulation of polymer nanocomposites." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/molecular-simulation-of-polymer-nanocomposites(56a195bb-81ed-4eb8-81d7-b3357d7f2316).html.
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Polymer nanocomposites (PNCs) are hybrid materials incorporating organic or inorganic nanoparticles (NPs) with at least one dimension in the submicron scale. Over the last two decades, these materials have drawn a remarkable attention due to their central role in industrial formulations and technological applications, extending from food packaging to smart coatings. Incorporating nanoparticles (NPs) to a polymer matrix can significantly alter the conformation and the mobility of the polymer chains in their proximity. Moreover, understanding the delicate balance between the enthalpic and entropic interactions is crucial to control and predict the ability of NPs to diffuse and disperse in the polymer matrix. The impact of these interactions on the structure and the dynamics of polymer chains and NPs is fully revealed in how a number of macroscopic properties changes, justifying the high interest on these materials for industrial applications. In this thesis, the impact on the structure, dynamics, viscosity and thermal conductivity of a number of microscopic properties is investigated by performing Molecular Dynamics (MD) simulations. Specifically, the PNC is represented by a coarse-grained model of a melt of linear homopolymer chains containing spherical NPs. Throughout this work, a number of parameters are modified in order to unveil possible patterns in the PNCâs performance. To this end, this work focuses on the consequences of modifying the NP size dispersity, NP-polymer chain relative size, and chainsâ degree of stiffness. Four theoretical models describing the diffusivity of NPs, three of which include nano-scale corrections, have been averaged to study the dependence of dilute NPsâ diffusivity on the NP polydispersity index. By comparing these models to the simulation results at different degrees of polydispersity, it is possible to obtain a more complete picture of their validity as compared to the monodisperse case. Regarding the diffusion of polymer chains, simulation results were in good agreement with the experimental results previously obtained by Composto and coworkers (Soft Matter 2012, 8, 6512), which relate the chainsâ diffusivity to the average interparticle distance. As far as the transport properties are concerned, they show a weaker dependence on the polydispersity index. By contrast, results on viscosity and thermal conducitivity show that they are conditioned by the polymer-NP specific interfacial area and the inverse average mass, respectively. These results are in good agreement with previous experimental results. A deeper examination of this intriguing deviation from viscosity predictions in traditional composites, reveals a non-trivial combination of thickening and thinning effects contributing to the final viscosity of the PNC. This thesis also address the influence of the chainsâ stiffness on the dynamical and viscous behaviour. An isotropic-to-nematic phase transition is observed, regardless of the NP-monomer interactions, below which a monotonic increase of both properties is observed, whereas orientationally ordered systems dramatically modify them, resulting into a steep increase or a smooth decrease depending on the direction in which they are measured.
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Li, Chengkai. "Computational design of polymer nanocomposites." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/230364/1/Chengkai_Li_Thesis.pdf.
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This project takes advantage of molecular dynamic simulation for the design of polymer nanocomposites. The newly synthesized low-dimensional carbon nanomaterials show unlimited potential in enhancing the mechanical performance of the polymer. The atomistic simulation approach enables a comprehensive characterization approach for the materials down to atomic level and establish in-detail insights into their mechanical behaviors usually beyond the reach of experiments. The obtained results and analysis establish a fundamental understanding of the enhancement mechanisms for the nanoscale reinforcements in polymer nanocomposites, which could eventually guide their design, fabrication, and engineering implementation.
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Xu, Jianhua. "Rheology of polymeric suspensions polymer nanocomposites and waterborne coatings /." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127317214.
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Smith, Jon Anthony. "Polyaniline Gold Nanocomposites." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4900.
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Polyaniline/Gold Nanocomposites
J. Anthony Smith
141 Pages
Directed by Dr. Ji and #345;?anata
The expectation that it is possible to create a range of new materials from two basic components, polyaniline fibers and gold particles is explored. Three synthetic methods were employed each of which created different materials and required different investigation techniques. The methods are: chemical, one step aniline oxidation / AuCl4- reduction; electrochemical/chemical, a two-step composite growth achieved by electrochemical polyaniline thin film growth followed by film immersion in AuCl4- solution and spontaneous reduction to gold particles; electrochemical, resulting in freestanding polyaniline thin film/Au nanoparticles carried out by electrochemical stripping of a polyaniline thin film grown over a sacrificial gold layer in the presence halide solutions. The incorporation of particles was shown to affect film morphology and electrical properties in all synthetic methods. The changes are in large part attributed to the development of a contact potential between the polyaniline and the gold particles. Applications for the composites include use as chemically sensitive layers, corrosion inhibition materials, and use as probes to evaluate nanoparticle substrate interactions.
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Bhaskar, Ajit. "Polymer-silicate and magnetic polymer nanocomposites processing and characterization /." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001201.
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Cudjoe, Elvis. "CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1497444919191893.
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Gunes, Ibrahim Sedat. "Analysis of Shape Memory Properties of Polyurethane Nanocomposites." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1247491380.
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Fogelström, Linda. "Polymer Nanocomposites in Thin Film Applications." Doctoral thesis, KTH, Ytbehandlingsteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12400.
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The introduction of a nanoscopic reinforcing phase to a polymer matrix offers great possibilities of obtaining improved properties, enabling applications outside the boundaries of traditional composites. The majority of the work in this thesis has been devoted to polymer/clay nanocomposites in coating applications, using the hydroxyl-functional hyperbranched polyester Boltorn® as matrix and montmorillonite clay as nanofiller. Nanocomposites with a high degree of exfoliation were readily prepared using the straightforward solution-intercalation method with water as solvent. Hard and scratch-resistant coatings with preserved flexibility and transparency were obtained, and acrylate functionalization of Boltorn® rendered a UV-curable system with similar property improvements. In order to elucidate the effect of the dendritic architecture on the exfoliation process, a comparative study on the hyperbranched polyester Boltorn® and a linear analogue of this polymer was performed. X-ray diffraction and transmission electron microscopy confirmed the superior efficiency of the hyperbranched polymer in the preparation of this type of nanocomposites. Additionally, an objective of this thesis was to investigate how cellulose nanofibers can be utilized in high performance polymer nanocomposites. A reactive cellulose “nanopaper” template was combined with a hydrophilic hyperbranched thermoset matrix, resulting in a unique nanocomposite with significantly enhanced properties. Moreover, in order to fully utilize the great potential of cellulose nanofibers as reinforcement in hydrophobic polymer matrices, the hydrophilic surface of cellulose needs to be modified in order to improve the compatibility. For this, a grafting-from approach was explored, using ring-opening polymerization of ε-caprolactone (CL) from microfibrillated cellulose (MFC), resulting in PCL-modified MFC. It was found that the hydrophobicity of the cellulose surfaces increased with longer graft lengths, and that polymer grafting rendered a smoother surface morphology. Subsequently, PCL-grafted MFC film/PCL film bilayer laminates were prepared in order to investigate the interfacial adhesion. Peel tests demonstrated a gradual increase in the interfacial adhesion with increasing graft lengths.QC20100621
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Rahmat, Meysam. "Carbon nanotube - polymer interaction in nanocomposites." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104648.
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Carbon nanotube–polymer nanocomposites have been the centre of intense studies for the past few years. With the superior properties of carbon nanotubes and the flexibility of polymers for different applications, extremely high expectations were set for this class of nanocomposites. Modelling studies showed significant potential, but the experimental investigations faced strict challenges to reach the predicted values. One of the main challenges is to obtain the optimum interaction between the nanotubes and the polymer matrix. The interaction influences the dispersion of nanotubes in the polymer and affects the overall properties of the nanocomposite. Therefore, the main objective of this research was to study the carbon nanotube–polymer interaction in nanocomposites. Based on a comprehensive review of the literature, molecular dynamics and atomic force microscopy were selected as the modelling and experimental techniques to study the interaction. In the modelling section, the interfacial properties of a single-walled carbon nanotube–poly(methyl methacrylate) nanocomposite were obtained through a three-phase simulation of a pull-out test. An interfacial binding energy of 0.39 kcal/molÅ2 was obtained from molecular dynamics simulation. On the other hand, in the experimental section, stepwise discretization method was proposed as a novel technique of interaction measurement using atomic force microscopy. Furthermore, a new interaction parameter, called interaction stress, was introduced to evaluate the interaction quality in nanocomposites. The stepwise discretization method was applied to a single-walled carbon nanotube–poly(methyl methacrylate) nanocomposite and a maximum interaction stress of 7 MPa was obtained. The results were, then, applied to classical contact theory and a nanoscale contact theory was developed. Furthermore, the interaction stress data were input to coarse grain simulations to obtain the interfacial properties of the nanocomposites. This new approach benefited from the flexibility of the coarse grain method and the reliability of the experimental data obtained from atomic force microscopy. Based on the results of the coarse grain simulations, the interfacial binding energy of a single-walled carbon nanotube–poly(methyl methacrylate) nanocomposite was estimated as 0.44 kcal/molÅ2. This value was then compared with the interfacial binding energy obtained from molecular dynamics results (i.e., 0.39 kcal/molÅ2). The good agreement between the results of modelling and experimental approaches demonstrated the validity of the work and the robustness of the proposed methods and parameters.Les nanocomposites avec des polymères renforcés de nanotubes de carbone ont été le centre d'attention de nombreuses études dans les dernières années. Les propriétés supérieures des nanotubes de carbone et la flexibilité des polymères à être utilisés dans de diverses applications ont créé de grandes attentes pour cette classe de nanocomposites. Des études de modélisation ont démontré un fort potentiel pour ces matériaux, cependant la validation expérimentale de ces propriétés prédites reste un défi. Une des principales difficultés est l'obtention d'une interaction optimale entre les nanotubes et la matrice polymère. Cette interaction influence la dispersion des nanotubes dans le polymère et affecte les propriétés globales du nanocomposite. De ce fait, l'objectif principal de ce travail de recherche a été l'étude de l'interaction entre les nanotubes de carbone et le polymère dans les nanocomposites. A partir d'une revue détaillée de la littérature, la méthode de dynamique moléculaire et la microscopie à force atomique ont été choisies comme techniques numériques et expérimentales pour étudier l'interaction. Dans la partie de modélisation, les propriétés d'interface d'un nanotube à paroi simple avec du poly(methyl methacrylate) ont été obtenues à partir d'une simulation d'un test d'arrachement en trois phases. Une énergie de liaison d'interface de 0.39 kcal/molÅ2 a été calculée par la simulation de dynamique moléculaire. Dans la section expérimentale, une méthode de discrétisation par étapes a été proposée en tant que nouvelle technique de mesure de l'interaction par microscopie à force atomique. De plus, un nouvel paramètre d'interaction, appelé contrainte d'interaction, a été introduit pour évaluer la qualité de l'interaction dans les nanocomposites. La méthode de discrétisation par étapes a été utilisée pour le nanocomposite de poly(methyl methacrylate) avec un nanotube de carbone à paroi simple, et une interaction maximale de contrainte de 7 MPa a été obtenue. Les résultats ont été ensuite utilisés pour la théorie classique de contact et une théorie de contact à l'échelle nano. Les données sur les interactions de contraintes ont été aussi utilisées comme entrées pour des simulations de dynamique moléculaire «gros grains» afin d'obtenir les propriétés d'interface des nanocomposites. Cette nouvelle approche bénéficie de la flexibilité de la méthode de dynamique moléculaire «gros grains» et de la fiabilité des données expérimentales obtenues par la microscopie à force atomique. À partir des résultats de la méthode de dynamique moléculaire «gros grains», l'énergie de liaison d'interface d'un nanocomposite de nanotube de carbone–poly(methyl methacrylate) a été estimée à 0.44 kcal/molÅ2. Cette valeur a été comparée à l'énergie de liaison d'interface obtenue par la méthode de dynamique moléculaire (i.e., 0.39 kcal/molÅ2). La bonne corrélation entre les résultats basés sur des approches numériques et expérimentales démontre la validité de cette étude ainsi que la robustesse des méthodes proposées et des paramètres développés.
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Wahab, Md Saidin. "Selective laser sintering of polymer nanocomposites." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496208.
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Wang, Yang. "Viscoelasticity of model aggregate polymer nanocomposites." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1027/document.
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Les nanocomposites polymères ont fait l'objet de recherches académiques et industrielles au cours des dernières décennies, du fait de leurs remarquables propriétés mécaniques et rhéologiques comparés aux polymères purs. En particulier, ils présentent du renforcement pour des fractions volumiques modérées, et des effets non linéaires pour des déformations relativement faibles. Malgré des décennies de recherche, la relation entre la rhéologie et la structure des nanocomposites est loin d'être comprise. Les simulations atomistiques peuvent donner une vision détaillée de l'interaction entre la dynamique des chaînes polymères et les charges renforçantes à une échelle locale. Cependant, il est difficile d'aborder les propriétés émergentes à une échelle mésoscopique, par exemple, simuler un grand nombre d'agrégats dans une matrice polymère enchevêtrée reste toujours hors de portée. Dans ce travail, nous proposons un modèle mésoscopique pour simuler la rhéologie des nanocomposites avec un fluide simple ou une matrice polymère enchevetrée, en utilisant la dynamique brownienne et la dynamique généralisée de Langevin, respectivement. Dans les deux dynamiques, le mouvement des chaines de polymère n'est pas décrit de façon explicite et son effet sur la dynamique de la charge est «moyenné». En utilisant ce modèle, nous étudions l'influence du type de charge, de leur taille, morphologie, et fraction volumique sur la rhéologie du composite modèle, ainsi que la morphologie des charges dans les simulations. Un cas particulièrement intéressant est celui d'agrégats quasi-fractals, qui peuvent être flexibles ou bien rigides. Nous démontrons que les systèmes avec agrégats présentent un renforcement significatif, qui augmente avec la taille des agrégats, leur rigidité, leur fraction volumique et leur polydispersité en taille. Une relaxation lente est également mise en évidence, et nous montrons qu'elle est liée à la rotation lente des agrégats. L'effet Payne, associé à la réponse non linéaire des modules dynamiques avec l'amplitude de déformation de cisaillement, est également observé pour nos modèles de composites. Nous faisons le lien entre l'arrangement microscopique des charges sous cisaillement et les propriétés macroscopiques du compositePolymer nanocomposites have drawn a lot of attention both from the academic and industrial research in the last decades, thanks to their remarkable mechanical and rheological properties as compared to pure polymers. In particular, they may display reinforcement for moderate volume fractions, and several non linear effects that appear for small deformation amplitudes. In spite of decades of research, the relation between nanocomposites structure and rheology is far from being understood. Atomistic simulations can give a detailed view of the interplay between polymer chains dynamics and fillers at a local scale. However, it is much more difficult to address the properties emerging at a mesoscopic scale, for instance, to simulate a large number of aggregates in an entangled polymeric matrix remains out of reach. In this work, we build a mesoscopic model to simulate the rheology of polymer nanocomposites with a simple fluid and an entangled polymer matrix, by using the Brownian dynamics and the generalized Langevin dynamics, respectively. In both cases, the motion of the polymer chains is not explicitly described and its effect on the filler dynamics is "averaged out". Using this model, we quantitatively determine the influences of the filler type, the filler volume fraction, size and morphology on the rheology of the model composite. Of particular interest is the case of fractal-like aggregates, which may be flexible or rigid. We demonstrate that model aggregates display significant reinforcement, which increases with the aggregate size, aggregate rigidity, filler volume fraction and polydispersity. Long relaxation times are also evidenced, which are related to the slow rotation of the aggregates. The well-known Payne effect, associated to the nonlinear response of the dynamic moduli with the shear deformation amplitude, is also seen in our model composites. We relate the behavior of microscopic filler to the macroscopic properties of the composite
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Saotome, Tsuyoshi. "Transparent polymer nanocomposites for aerospace applications." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1970611211&sid=54&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Winter, Allen Douglas. "NEXAFS spectroscopy studies of polymer nanocomposites." Thesis, Bangor University, 2017. https://research.bangor.ac.uk/portal/en/theses/nexafs-spectroscopy-studies-of-polymer-nanocomposites(25f9b2a7-9b79-48a1-8b80-c910bc678a21).html.
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Polymer nanocomposites, with the huge range of property sets (both structural and functional) they can exhibit, could pave the way towards “materials by design”—one of the promises of nanotechnology. Hindering the mass adoption of polymer nanocomposites is a limited understanding of the complex relationship between processing steps, structural parameters at the nanoscale, and resulting macroscale bulk properties. To this end, the work presented in this thesis reports on the investigations of four polymer nanocomposite case studies, each addressing effects of different variables, through NEXAFS spectroscopy—a synchrotron technique that offers rich chemical and structural information. In the first case study, non-covalent interactions resulting from electrospinning of a polymer blend of polydimethylsiloxane–poly (methyl metacrate) filled with carbon nanotubes are addressed, as well as effects of nanofiller diameter. The second study investigates the thermoactive behaviour of ethylene vinyl acetate j multiwall carbon nanotube composites through in situ temperature-resolved NEXAFS spectra, and an actuation mechanism is proposed. The third case study explores ageing effects of this thermoactive nanocomposite, and reports on the lifetime of non-covalent interactions. Finally, the fourth case study explores the effects of excessive sonication, which is seen here to drastically damage nanofiller and resulting matrix–filler interactions. This work represents four additional points in a growing dataset from other studies of polymer nanocomposites that—when sufficiently populated—could be mined through clustering algorithms and machine learning approaches to extract the elusive processing–structure–property link, which will enable the wide-spread exploitation of polymer nanocomposite technology.
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Scocchi, Giulio. "Multiscale simulation of polymer-clay nanocomposites." Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3098.
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2007/2008The main subject of this thesis consisted in the development of a multiscale procedure for the simulation of polymer – layered silicate nanocomposites (PLSN). The final objective was to provide a concrete support to in the component selection stage in new materials design process. In particular, polymer/silicate interface characteristics have been studied by using MD (Molecular Dynamics) techniques, aggregated platelet structure (stacks) by using the DPD (Dissipative Particle Dynamics) method, while macroscopic models have been built and analyzed using a FEM (Finite Element Method) based approach. Our sequential multiscale scheme allowed us to successfully predict Young’s modulus for different PLSN systems.
L’argomento di questa tesi consiste nello sviluppo di una procedura multiscala per la simulazione di nanocompositi polimero – silicati lamellari. L’obiettivo finale è quello di realizzare un efficace strumento di supporto per la fase di selezione dei componenti nel processo di design di nuovi materiali. In particolare, le caratteristiche di interfaccia tra polimero e silicato sono state studiate con tecniche di Molecular Dynamics (MD), le strutture composte da aggregati di lamelle (stacks) con il metodo Dissipative Particle Dynamics (DPD) mentre i modelli macroscopici sono stati creati e analizzati utilizzando un approccio basato sul metodo FEM. La procedura multiscala così ottenuta ci ha permesso di prevedere con successo il modulo di Young per diversi sistemi polimero – silicati lamellari.
XXI Ciclo
1978
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Zhang, Guoqiang. "The Synthesis and Electrical Properties of Functional Polymer Nanocomposites." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case149010222646324.
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Mulliken, Adam Dustin 1979. "Mechanics of amorphous polymers and polymer nanocomposites during high rate deformation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38265.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 275-290).
It has been suggested that a polymer's macroscopic mechanical response to a general loading case is governed by its ability to access various primary and secondary molecular mobilities. Specifically, under conditions of high strain rate, restricted secondary molecular motions are thought to bring about enhanced stiffness and strength. In accordance with this theory, an experimental protocol and associated analytical techniques were established to better understand the rate- and temperature-dependent mechanical behavior of two exemplary amorphous polymers, PC and PMMA. The experiments included dynamic mechanical thermal analysis (DMTA), as well as uniaxial compression tests over a wide range of strain rates. In both cases, the polymer exhibited a distinct transition in the rate-dependent yield behavior, under the same temperature/strain rate conditions as the observed viscoelastic 0-transition. Drawing off of previous research in the field of polymer mechanics, a new continuum-level constitutive model framework is proposed to account for the contributions of different molecular motions which become operational in different frequency/rate regimes. This model is shown to capture well the unique rate-dependent yield behavior of PC and PMMA, as well as the compressive stress-strain response under isothermal conditions.
(cont.) Through the rest of the thesis, additional features are integrated into the model to allow for more accurate predictions of mechanical response under high-rate, impact loading. Adiabatic conditions are captured by considering the heat evolved during dissipative plastic deformation. The corresponding temperature rise predicted by the model is corroborated by experimental measurements obtained via infra-red techniques during the split-Hopkinson bar test. In conjunction with the implementation of adiabatic heating, the model's kinematic framework is altered in order to also capture the effects of thermal expansion. Finally, drawing off of existing experimental data in the literature, the implementation of pressure-dependence in the model is revised. In the final portion of this thesis, the generality of the experimental and theoretical methods is explored. The techniques are applied in the study of the rate-dependent mechanical behavior of a variety of polymer-based material systems, including a PC-POSS nanocomposite, homopolymer PVC, a plasticized PVC, and a PC-triptycene co-polymer. In every case, the methods garnered important insight into both macroscopic phenomena and the molecular mechanisms of deformation resistance.
by Adam Dustin Mulliken.
Ph.D.
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Wei, Yuan. "Probing Local Structure and Dynamics of Polymer Brushes with Neutron Scattering." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1624963009022896.
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Kim, Yeon Seok. "Electrical conductivity of segregated network polymer nanocomposites." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1880.
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Consiglio, Armando. "Molecular dynamics simulations of conducting polymer nanocomposites." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18454/.
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Among the conducting polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most used materials in the field of bioelectronics due to its biocompatibility, chemical stability and high electronic as well as ionic charge transport mobilities.
Despite many experimental findings, a microscopic understanding of the materials electronic properties is currently elusive; the main reason is the lack of structural atomistic data of the polymer blend, that is, difficult to obtain because of the disordered and nano-crystalline morphology.
In this thesis work we develop and use Molecular Dynamics based methods to simulate the structure of PEDOT:PSS in presence of an interface, investigating how a surface and some physical quantities (temperature, water content and electric charge on PEDOT oligomers) would introduce order to the evolving structure, and pointing out the differences between interfacial and bulk behaviour. The results obtained by computer simulations are used to estimate experimentally accessible parameters and to compare them with already existing experimental data.
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Chu, Chun. "Development of polymer nanocomposites for automotive applications." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37128.
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Polymer nanocomposites (PNCs) have gained significant interest because they have outstanding performance that allows cost reduction, weight reduction, and product improvement. This research study focuses on the manufacture and characterization of PNCs in order to explore their potential in automotive applications. More specifically, polypropylene (PP) nanocomposites reinforced with xGnP and nanokaolin were fabricated by manufacturing methods that optimize their performances. Exfoliated graphite nanoplatelets (xGnP) are promising nanofillers that are cost effective and multifunctional with superior mechanical, thermo-mechanical and electrical properties. Nanokaolin is a newly introduced natural mineral mind in Georgia that has not been studied as of now. PNCs reinforced with these two nanofillers were characterized in terms of mechanical, thermo-mechanical, and various other properties, and then compared to talc- reinforced PP composites, which are the current state of the art for rear bumpers used by Honda Motor. Characterization results indicated that xGnP had better performance than talc and nanokaolin. Furthermore, the addition of xGnP introduces electrical conductivity in the PNCs, leading to more potential uses for PNCs in automotive applications such as the ability to be electrostatic painted. In order to fabricate PNCs with a desired conductivity value, there is need for a design tool that can predict electrical conductivity. Existing electrical conductivity models were examined in terms of model characteristics and parameters, and model predictions were compared to the experimental data. The percolation threshold is the most important parameter in these models, but it is difficult to determine experimentally, that is why a correlation between thermo-mechanical properties and electrical conductivity is also investigated in this study.
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Zeng, Qinghua Materials Science & Engineering Faculty of Science UNSW. "Fundamental studies of oganoclays and polymer nanocomposites." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2004. http://handle.unsw.edu.au/1959.4/20657.
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Polymer materials are commonly reinforced with organic or inorganic fillers to improve their mechanical properties and to reduce the cost. Such reinforcement strongly depends on the characteristics of fillers (e.g. size, shape, aspect ratio and surface feature) and their dispersion in polymer matrix. The use of inorganic fillers exploits the synergistic effect of high mechanical strength and heat durability of fillers and processing ease of polymers. However, it often causes interfacial incompatibility and an increase in density and a loss of tenacity and opacity. Because layered clays possess rich intercalation chemistry and can be delaminated into disk-like nanopartciles, we investigate the possibility of developing polymer nanocomposites from montmorillonite (MMT). As a result, two nanomaterials, intercalated polyaniline (PANI) nanocomposites and exfoliated PS nanocomposites, have been fabricated via in situ polymerization. Morevoer, experimental work shows that the surface modification of clays and the dispersion of organically modified clays (i.e. organoclays) are crucial to the success of fabricating polymer nanocomposites. Therefore, molecular dynamics (MD) simulations are used to investigate such fundamental aspects on the structure and dynamics of organoclays and the interfacial interactions and structure of diblock copolymer (i.e. PU) nanocomposites. The simulated results are in good agreement with the available experimental data. For organoclays, the results indicate that the alkyl chains exhibit strong layered structures in the interlayer space of clays. Such layering behaviors strongly depend on the chain length and layer charge. More importantly, a pseudo-quadrilayer structure is observed for organoclays modified with dioctadecyldimethyl ammoniums in which the alkyl chains do not lie flat within a single layer but interlace and spread into the adjacent layers. Finally, different orientaion of chain segments is found in the middle and end segments, and within and out of the layer structure. For polyurethane (PU) nanocomposites, van der Waals interaction between apolar alkyl chains and PU soft segments dominates the interactions between organoclay and PU. In addition, hydrogen bonding can form between the siloxane oxygen of clay surface and nitrogen (hard segment) or oxygen (soft segments) of PU. Furthermore, there is no distinct phase-separated structure for PU in the nanocomposites, which is attributed to the results of competitive interactions among PU, alkyl ammonium and clay surface.
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Zhao, Qian Samulski Edward T. "Co2-mediated formation of polymer/clay nanocomposites." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,251.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Do ctor of Philosophy in the Curriculum in Applied and Materials Sciences." Discipline: Applied and Materials Sciences; Department/School: Applied and Materials Sciences.
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Du, Ying. "Fabrication and characterization of particulate polymer nanocomposites /." View online ; access limited to URI, 2007. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3284823.
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Kato, Ryo. "Interfacial interactions in polymer layered silicate nanocomposites." Thesis, Manchester Metropolitan University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491172.
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Polymer layered silicate nanocomposites (PLSN) have attracted great interest because they exhibit remarkable improvements in materials properties relative to pristine polymers. Successful formation of a PLSN is critically dependent on generation of very high interfacial area in the composite. This is accomplished when the stacks of silicate platelets (tactoids) split into discrete platelets. The latter phenomenon is known as exfoliation and is strongly influenced by interfacial chemistry (i.e. structure and properties of the interface or interphase) associated with the edge and basal surfaces of the silicate platelets, chemical modification (usually with quaternary alkyl ammonium halides) of the latter and the resulting effect on interactions between the platelets themselves and polymer chains. Interactions between sodium montmorillonite (Na-MMT)/organically modified montmorillonite (o-MMT) and a variety of probes, some of which are intended to model the structures present in the components of a polyurethane (PU), epoxy resin and polystyrene system (PS), have been studied. The adsorption process was characterised using flow microcalorimetry (FMC) in conjuncqon with diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and wide angle x-ray scattering (\VAXS). Adsorption of hydrogen bondable groups, such as alcohol, ether, amine probes, onto Na-MMT was dominated by the hydrogen bonding interactions with hydrated Na+ ions and with the hydroxyl groups present at the platelet edges. Moreover, stronger interactions with hydrated Na+ ions led to greater retention of the probes after the desorption process. When the Na-MMT was moisturized at ambient atmosphere, hydrogen bondable probes showed a reversible adsorption. In contrast, chemical adsorption (reaction) dominated the adsorption of the isocyanate probe onto Na-MMT; the latter reacted either with the platelet edge hydroxyl groups forming a urethane linkage or with pre-adsorbed ambient water molecules adsorbed onto Na-MMT ultimately forming a physically adsorbed urea. In the case of o-MMTs, when only the platelet edge hydroxyl groups were available, hydrogen bondable probes showed a reversible adsorption. Reactions between reactive probes, including isocyanate and epoxide probes, and surfactant functional groups (OH and COOH groups) are affected by the gallery structures, such as the arrangement of surfactant within the galleries and level of surfactant intercalated. Adsorption of aromatic probes, including styrene, ethylbenzene and polystyrene, was dominated by the relatively weak dispersive interactions with the basal surfaces of o-MMT, and was significantly affected by the gallery structures ofo-MMT (surfactant level and surfactant structure). This study has provided valuable new insight into interactions in nanocomposite materials.
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Carreyette, Shuaijin Chen. "Solid intercalation to produce polymer/clay nanocomposites." Thesis, Nottingham Trent University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396366.
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Lander, Julie-Anne. "Structure development in silicate-layered polymer nanocomposites." Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/4390.
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The demands made of materials have resulted in the formation of complex composite structures; one such example of these is nanocomposites. This study is primarily devoted to the preparation and characterisation of nanocomposites. Reactively cast and reactively extruded nanocomposite strategies for the preparation of polyamide-6 composites were compared. The catalyst and activator system selected was based on an industrially successful combination. The extruder screw and barrel configuration used had previously been proven effective for the reactive polymerisation of polyamide-6. The principal objectives were the investigation of the influence of layered-silicates on both the microstructure and the physical properties of the composites. As well as the analysis of the mechanisms that influence the physical performance of the materials produced. The characterisation of the filler-matrix microstructure and its effect on physical properties of the composites were investigated using a range of chromatographic, microscopic, thermal and X-ray analytical techniques. Selected mechanical properties were measured using standard test procedures. Therefore results obtained and subsequent trends observed in reaction cast and reaction extruded nanocomposites could be compared and contrasted. The influence of the polymerisation conditions, residual monomer content and the nature of the composite structure produced were considered. It was observed that the nature of the matrix crystalline structure could be greatly influenced by the material composition, method of preparation and processing technique. The crystal form of the spherulites present appeared to be the key factor in influencing mechanical strength. The treatment of the silicate-layered clay successfully increased the inter-layer spacings, which was further increased by the presence of high shear forces.
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Lew, C. Y. "Polymer-clay nanocomposites : preparation, processing and properties." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419556.
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Ploszajski, Anna. "Polymer-hydride nanocomposites for portable hydrogen storage." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10041608/.
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It has been nearly fifty years since the idea of the hydrogen economy – an energy landscape centred on hydrogen as the energy vector – was proposed. A major difficulty in realising the hydrogen economy has been hydrogen storage, particularly for the portable applications for which this energy-dense fuel is so attractive. For these applications, solid-state approaches to hydrogen storage are a good alternative to gas cylinders, from a volumetric and weight perspective. This thesis focuses on one particular material; a composite made from ammonia borane and polyethylene oxide (AB-PEO). A major finding from this project was that the ABPEO material is a cocrystal-forming system, the first to be recognised as a hydrogen storage material. The kinetics and mechanism of formation of the cocrystal phase have been investigated. The molecular structure of an AB-PEO cocrystal polymorph has been ascertained, and this experimentally proved what was only previously computationally predicted; that hydrogen bonds form between AB and PEO. These hydrogen bonds have been found to encourage hydrogen release from the AB molecules by promoting the formation of key reaction intermediates when the material is heated. This modification of the hydrogen release pathway results in lower hydrogen release temperatures but an increase in the levels of volatile gaseous impurities released alongside the hydrogen. However, a major beneficial effect of PEO on AB is the suppression of the bubbling and foaming which usually accompanies hydrogen release from AB. In this work, advanced time-resolved 3D imaging techniques have been used to observe and quantify the microstructural pore dynamics during hydrogen release from pellets made from AB-PEO composites. These experiments, never before used in the context of hydrogen storage, provide key insights to allow materials engineers to manufacture solid-state hydrogen storage materials into working portable systems.
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Erguney, Fatih M. "COARSE-GRAINED MC SIMULATIONS OF POLYMER NANOCOMPOSITES." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1176404164.
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Chang, I.-Ta. "Excimer Laser Ablation of Polymer-Clay Nanocomposites." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1333995807.
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Zeng, Changchun. "Synthesis, Structure And Properties Of Polymer Nanocomposites." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1078245607.
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Pollard, Rick A. "Processing and Characterization of Polymer Based Nanocomposites." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1331297125.
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Sheng, Xia. "Polymer nanocomposites for high-temperature composite repair." [Ames, Iowa : Iowa State University], 2008.
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Kothurkar, Nikhil K. "Solid state, transparent, cadmium sulfide-polymer nanocomposites." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006485.
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Wilson, Jessica L. "Synthesis and magnetic properties of polymer nanocomposites." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000380.
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